The present invention relates to a pusher device for positioning the ends of plastic optical fibers, and more particularly to a pusher device employable for a multiple-core optical fiber cable incorporating plural plastic optical fibers.
FIGS. 8 and 9 show a pusher device employed for a dual-core optical fiber cable in the prior art. As shown in FIGS. 8 and 9, an optical fiber cable 1 is constituted of two plastic optical fibers 2 and 3 having different flows, sheaths 4 and 5 made of polyethylene, etc. for covering the respective optical fibers 2 and 3, and an outer cover 6 made of polyvinylchloride, etc. for generally covering the sheaths 4 and 5. The sheaths 4 and 5 are exposed at the end portion of the optical fiber cable 1, and are held by a pair of pusher members 8 and 9 of a pusher device 7 to position the ends of the optical fibers 2 and 3. The optical fibers 2 and 3 are projected from the end surfaces of the sheaths 4 and 5 at a predetermined amount. The end surfaces 2a and 3a of the optical fibers 2 and 3 are arranged in opposed relation with an optical connector (not shown) so as to transmit an optical signal.
As shown in FIG. 8, the conventional pusher device 7 is designed so that the two sheaths 4 and 5 are sandwiched between opposed flat surfaces 8a and 9a of the pair of pusher members 8 and 9, and are held by applying a clamping force thereto in the direction of an arrow shown in FIG. 9, thereby enhancing a frictional force between the optical fiber 2 and the sheath 4 and a fricitional force between the optical fiber 3 and the sheath 5, and preventing slippage of the end surfaces 2a and 3a of the optical fibers 2 and 3.
However, in the aforementioned pushed device 7 having the structure that the sheaths 4 and 5 are held by the flat surfaces 8a and 9a of the pair of pusher members 8 and 9, slip of the optical fibers 2 and 3 relative to the sheaths 4 and 5 has not been securely prevented unless the clamping force of the pusher members 8 and 9 is much great. If the clamping force of the pusher members 8 and 9 is increased so as to securely prevent the slip of the optical fibers 2 and 3, there will be generated local stress concentration to remarkably reduce light transmittance of the optical fibers 2 and 3. As a result, the conventional pusher device 7 has not securely prevented the slip of the optical fibers 2 and 3 without reducing the light transmittance too much. Under the condition where the end portions of the optical fibers 2 and 3 are liable to slip in the respective sheaths 4 and 5, when the optical fiber cable 1 is bent near the end portion thereof as shown in FIG. 9, the end surfaces 2a and 3a of both the optical fibers 2 and 3 are slipped from a predetermined position because of difference in curvature. For example, the end surface 2a of the optical fiber 2 on the side of smaller curvature in FIG. 9 is projected from the predetermined position, and is brought into abutment against the optical connector (not shown) to cause a serious accident such as damage of the end surfaces.